Alberts B. The Molecular Biology of The Cell 4th ed. Finazzo, S. King, D. Epithelium Study Guide. Tamarkin, D. Glomerular Filtration. Simple Squamous Epithelium Structure. Simple squamous epithelial cells are thin and flat the thinnest of all epithelial cell-types , which allows them to have a large surface area that is exposed to the lumen on one side the apical surface , and to the basement membrane i.
This is called pseudostratified , columnar epithelia. This cellular covering has cilia at the apical, or free, surface of the cells. The cilia enhance the movement of mucous and trapped particles out of the respiratory tract, helping to protect the system from invasive microorganisms and harmful material that has been breathed into the body. Goblet cells are interspersed in some tissues such as the lining of the trachea.
The goblet cells contain mucous that traps irritants, which in the case of the trachea keep these irritants from getting into the lungs. Figure 4. Pseudostratified columnar epithelia line the respiratory tract. They exist in one layer, but the arrangement of nuclei at different levels makes it appear that there is more than one layer. Goblet cells interspersed between the columnar epithelial cells secrete mucous into the respiratory tract. Transitional or uroepithelial cells appear only in the urinary system, primarily in the bladder and ureter.
These cells are arranged in a stratified layer, but they have the capability of appearing to pile up on top of each other in a relaxed, empty bladder, as illustrated in Figure 5. As the urinary bladder fills, the epithelial layer unfolds and expands to hold the volume of urine introduced into it.
As the bladder fills, it expands and the lining becomes thinner. In other words, the tissue transitions from thick to thin. Figure 5. Transitional epithelia of the urinary bladder undergo changes in thickness depending on how full the bladder is. Improve this page Learn More. Skip to main content. Module Animal Diversity. Simple secretory columnar epithelium lines the stomach and uterine cervix.
The simple columnar epithelium that lines the intestine also contains a few goblet cells. In histological slides of pseudostratified epithelium , it looks as though some of the cells are not in contact with the basal lamina, and the nuclei are at different levels. So it looks as though there is more than one layer of cells. However EM shows that all the cells contact the basal lamina, so this is a 'simple' epithelium.
But it is called pseudostratified, because of its appearance. Pseudostratified ciliated columnar epithelium containing goblet cells lines most of the major airways.
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